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Not with that attitude.

Just do it. Make what you want. Nobody gives a shit who you are or how old you are. What they will care is if you make something worthwhile or not. If you want to make something, make something. Don't spend an entire sentence wasting people's time about how you prefer to misspell a word.  The only reason anyone would even know you are 13 is because you made a post about it (and also because your mode of speech betrays that just a bit). Just shut up and make something. If it's stupid, you'll find out. If it's worthwhile, the community will let you know. Whether you're 13, or interested in sex, or have a good relationship with your mom, or like to misspell words is completely meaningless compared to what you create.

Just make something. I'm not trying to be mean, I'm trying to give you some motivation. Don't bother what people say you can create. That's not art. As soon as you care that somebody tells you that you aren't allowed to make something, you are no longer an artist. An artist creates because they have to... because they know no other way to exist. An artist will find a way to create even if no one will allow them. Hell, if you need a hand, let me know. If you are actually creating something of value and not just, as most of the people who responded seem to think based on what you've written, some meaningless juvenile crap, then it doesn't matter how old you are... what matters is that art deserves to get made.

So before you concern yourself with whether or not you can or should make something based on how old you are, the question should be this... does what you want to make deserve to get made? If so, then you would be OBLIGATED to make it, even if you were only 7. Just don't confuse what your juvenile mind thinks deserves to get made with what actually is worthwhile. Most people your age think they have a clear understanding of the universe, but that's only because everyone at every stage of life feels like what they think is the only thing that is correct. This is related to what's known as the Dunning-Kruger effect. People think that what they know is the height of knowledge because they don't actually know how much there actually is to know. Don't be upset if you pour your heart and soul into some game, call it "adult concepts," and have adults snub it. If you are 13 years old, you will probably have a much better time making things that are meant to show your own point of view from your perspective rather than trying to make something you think will be deep for everyone. An adult would enjoy your game more if they knew they were spending some time looking at things from your perspective, rather than having you say "I'm thirteen and I think this is deep," because that will result, most likely, in scorn before people even bother to play the game... they simply will not believe that what you think is deep is worth their time. 

It's all about perspective. 

You asked specifically about creating adult stuff.